| Poultry manure (PM) contains nutrients that are highly beneficial for crop production, but loss of nutrients, pathogenic bacteria, hormones, and other PM constituents to groundwater and surface waters can disrupt aquatic ecosystems, raise concerns for recreational water users, threaten drinking-water systems and human health, and have economic consequences for producers. The principle objective of this study was to compare the effects of poultry manure application rate and tillage practices (chisel-plow and no-till) on drainage tile-water quality. The secondary objective was to further understand the processes and pathways which impact the fate and transport these contaminants. While the focus of this dissertation is on fecal indicator bacteria ( Escherichia coli and enterococci), the pathogen, Salmonella , and phosphorus, concentrations of nitrate and hormones in tile-water samples were also assessed. Results of this research can be used to inform farm-management decisions and watershed planning efforts.;To determine the effect of manure application rates and tillage on bacteria concentrations in tile-waters, water samples were collected weekly from drainage tile outlets and following precipitation events from 30 days before manure application to 100 days post application, when tiles were flowing. In 2011 and 2012, additional tile monitoring was employed to capture the hydrographic response to precipitation, and in 2012, smoke-testing was used to determine macropore densities.;To determine whether over-wintering of bacteria had occurred, soil samples were obtained each spring at 0-15 cm and 15-30 cm depths. In 2012, soil samples were collected 21, 42, and 158 days after manure application (DAM), to assess the effects of time, manure application rates, and tillage on frequency of detection and concentrations of bacteria. Detection of all three bacteria species in spring soil samples indicated over-wintering of bacteria was possible.;Soil and tile-water samples were also used to determine the effects of manure application rate and tillage on orthophosphate (PO4-P) losses to tile drainage waters. Spring soil samples (0 -- 15 cm and 15 -- 30 cm) were analyzed for soil test phosphorus (STP) using the Bray's 1-P method. Water samples were obtained from drainage tiles following precipitation events in 2010 and 2011, and more frequent sampling throughout selected hydrograph events was conducted in 2011 and 2012.;In general, this study shows that applying poultry manure at a low (∼112 kg/ha N) application rate to chisel-plowed ground is likely to result in smaller bacteria and orthophosphate losses to tile-waters than application at a higher rate (∼224 kg/ha N) on no-till plots. Even when heavy manure application and no-till practices were combined, tile-waters only exceeded recreational water quality standards (which do not apply directly to tile outlets) for E. coli under exceptionally wet conditions. However, results of this study also show that Salmonella can be present in waters containing little or no fecal indicator bacteria.;Producers and watershed managers can take away several important lessons from this research. This study confirms what is already widely accepted, that using lower application rates for poultry manure, and using fertilizers with lower levels of P to balance crop needs, would reduce contaminant losses, benefitting both producers and the environment. An increase in tillage, on the other hand, increases the risk of runoff and soil compaction, and may have other drawbacks; therefore, more modest changes to tillage, such as occasional disking, may be recommended to reduce bacterial water quality impacts by disconnecting macropores and helping to distribute phosphorus within the soil column. Control of pH, and other techniques for increasing the ability of soils to retain phosphorus, may prevent losses to tiles as well as surface-runoff. Furthermore, transport of bacteria and phosphorus via tile drainage should be considered when designing watershed models and water quality improvement plans. (Abstract shortened by UMI.). |
